1. Technical Field
The present invention relates to a sensor unit and a motion measurement system or the like using the sensor unit.
2. Related Art
According to the related art, when a measurement device such as a motion sensor which detects acceleration, angular velocity and the like is mounted on a measurement target such as sporting equipment, a shock and vibration absorber is arranged between the measurement device and the measurement target. As the shock and vibration absorber damps a shock and vibration from the measurement target, the measurement device carries out accurate measurement without being affected by the shock and vibration.
According to JP-A-1-302169, a buffer is mounted on an outer surface of an exterior package of an acceleration sensor, thus preventing the sensor from being damaged by a fall when the sensor is carried around. The literature discloses the acceleration sensor can be mounted on a vehicle via the buffer.
According to JP-A-3-170065, on a first member with high mechanical strength which supports a substrate of an acceleration sensor, a buffer is provided parallel to a connector unit. As the connector is connected to a main body unit, the buffer is laid between the acceleration sensor and the main body unit.
According to JP-UM-A-7-008775, an elastic cover body with high shock absorptivity covers a housing of an acceleration sensor. According to JP-A-9-145738, a buffer is provided between an acceleration sensor and a substrate.
However, JP-A-1-302169 to JP-A-9-145738 do not disclose a structure to install a sensor portion such as an acceleration sensor onto sporting equipment.
FIG. 1 shows a comparative example in which when a sensor portion 2 is mounted on sporting equipment, for example, on a mounting surface 1b provided at a grip end 1a of a tennis racket 1, a shock and vibration absorber 3 is provided as in-between, as in JP-A-1-302169 to JP-A-9-145738. In the case where a motion of the tennis racket 1 is measured by the sensor portion 2, the shock and vibration absorber 3 can be provided as in-between as in the comparative example of FIG. 1 in order to prevent direct transmission of a shock and vibration generated when the tennis racket 1 strikes a ball to the sensor portion 2.
Here, in order for the shock and vibration absorber 3 to absorb a strong shock and vibration at the time of striking, it is necessary to increase the volume of the shock and vibration absorber 3 or switch to a material that can easily absorb a shock and vibration.
However, if the volume of the shock and vibration absorber 3 is increased, for example, as shown in FIG. 2, the shock and vibration absorber 3 becomes heavier, making the whole racket 1 heavier and also changing weight balance of the tennis racket 1. The shock and vibration absorber 3 protruding as shown in FIG. 2 becomes an obstruction when a user holds the grip of the tennis racket 1.
Meanwhile, if the material of the shock and vibration absorber 3 is softened so that the material can easily absorb a shock and vibration, as shown in FIG. 3, the sensor portion 2 itself swings, for example, in the direction of arrows shown in FIG. 3 and cannot measure the motion of the tennis racket 1 accurately.